Most trailers and older vehicles are designed with leaf spring supported suspension systems. Leaf springs comprise several metal strips joined to act as an elastic spring. The axle is coupled to the frame by a pair of leaf springs to provide flexible support. The leaf springs provide the suspension system for the trailer and allow the trailer to ride more smoothly on rough grounds. Though newer cars are manufactured with more sophisticated suspension systems, trailers are most often manufactured with leaf springs.
Leaf springs generally perform well as a rugged and durable suspension system but have been known to fail. Leaf springs fail for a number of reasons including: age, material quality and load size. When a leaf spring fails on a typical trailer, the frame is no longer vertically supported by the leaf spring coupled to the axle. The weight of the trailer then falls directly onto the tire. In addition to loss of vertical support, the trailer axle no longer has longitudinal support with respect to the frame.
Loss of vertical and longitudinal support poses a risk of injury to persons and property. Without vertical support, the trailer frame may come into contact with the axle. Further, the wheel well may come into contact with a rapidly rotating tire. This contact between a wheel well and a rapidly rotating tire causes damage in a number of ways including: the tire is shredded; the wheel is bent; and the intense friction damages the wheel well and the paint on the trailer. Loss of longitudinal support causes the axle to torque with respect to the trailer frame. Again, this could result in the tire coming into contact with the trailer frame or wheel well. When vertical and longitudinal support are lost, the driver could lose control of the trailer or vehicle. In rare instances, the axle may cause the trailer to catapult into the air.
In the course of an average leaf spring failure, the driver may notice the trailer or vehicle exhibiting peculiar behavior such as fish tailing, dragging or riding at an uneven height. Generally, once the driver notices the leaf spring malfunction it is too late to prevent damage. Further even if the driver notices the leaf spring malfunction and is able to pull over to the side of the road before extensive and disabling damage is done to the tires, wheels and frame, the trailer is inoperable in that state. A common make-shift solution for drivers in this plight is to jack up the trailer frame and place blocks of wood or the like between the frame and the axle. These blocks act as spacers between the axle and the frame so that the tires will not rub against the frame or wheel wells. Sometimes duct tape, rope or other fastening material is used to hold the spacer blocks in place longitudinally. Using this temporary solution, the disabled driver limps home with the trailer or vehicle, often with more failures and subsequent re-adjustments along the way.